Process and apparatus for dewaxing oils



June 2, 1936.

B. G. ALDRIDGE ET AL PROCESS AND APPARATUS FOR DEWAXING OILS 2 Sheets-Sheet l Filed Sept. 18, 1933 I! ll fill III/l1) KIM W mm Y TH M, mu m ww n 5 A a e mu, 1

A aw {m June 2, 1936. I B. G. ALDRIDGE ET AL v 2,042,758

PROCESS AND APPARATUS FOR DEWAXING OILS atented June 2, 1936 PATENT OFFICE PROCESS AND APPARATUS FOR DEWAXING OILS Blair G. Aldridge, Los Angeles, and Basil Hopper,

San Pedro, Califi, assignors to Union Oil Company of California, Los Angeles, Calif., a corporation of California f A Application September 18, 1933, Serial No. 689,976

13 Claims. (Cl. 204-24) This invention relates to wax separation from wax-bearing oils, and, more particularly, it relates to the separation of precipitated wax from a suspension thereof in oil.

Many crude oils containing paraffin or wax are employed to produce lubricating oils. The paraflin or wax is frequently found associated with the lubricating oil fractions of paraifin base crude oils and of asphalt base crude oils, as well as in mixtures or blends of lubricating oil fractions obtained from both paraflin and asphalt base crude oils. The wax is not only of doubtful lubricating value, but it also limits the minimum temperature at which lubricating oils containing it can be used. This is due to the congealing of such wax containing oils at the lower tempera tures. Therefore, in the production of lubricating oils from petroleum fractions containing wax or paraflin, it is customary to remove a substantial portion of the wax or paraffin present in the oil in order to lower its pour point, or the temperature at which the oil congeals.

Separation of wax from wax-bearing oils or fractions thereof has been accomplished in the past by several processes, all of which more or less objectionable and inefiicient.

Thus, the so-called cold settling process, wherein the wax-containing oil is first diluted with a quantity of a light hydro-carbon fraction, such as naphtha, gasoline, etc., then slowly chilled by suitable refrigerating means for a period of to 50 hours until the desired low temperature is reached, and then allowed to stand for a period of several weeks to allow the wax precipitated out of solution by such temperature lowering to settle to the bottom of the chilling tank, is obviously undesirable in view of the cost of refrigeration for the necessary long periods of time, the large capacity of refrigeration and storage equipment, and the poor separation of wax and oil obtained during such settling.

Also. the so-called cold pressing process, in

' which the chilled wax-containing oil, having the precipitated wax in suspension therein, is pumped through a filter press under a pressure of 300 to 350 pounds per square inch, is objectionable in view of the frequent cleanings of the filters made necessary by the clogging thereof by the separated wax. Furthermore, it has been found extremely diflicult and highly impractical to treat by this method the oils containing amorphous and/or micro-crystalline wax.

Recently a method has been developed for separating electrically the wax which has been precipated from a wax-containing oil. According to this method, the wax-containing oil or a fraction thereof is diluted with a light hydrocarbon fraction, then chilled to the proper temperature at which the wax precipitation takes place, and

the mixture of oil, diluent and precipitated wax is finally subjected to an electric field or electric current to aid separation and deposition of the wax from this mixture. The treatment of the wax-oil-diluent mixture according to this process causes the wax to deposit on the electrodes. In the case of some waxes i. e., those which appear to be negatively charged, the deposition occurs on the positive electrode. If the wax is positively charged it deposits on the negative electrode. However, oftentimes the wax is found deposited on both electrodes.

In operating according to the aboye-described method it has been found that the potential gradient of the electric current must be comparatively high, voltages of from 5,000 to 35,000 volts per inch, either continuous or interrupted direct current, through the solution having been found effective in agglomerating and depositing the precipitated wax. Furthermore, it has been found that time is an essential element. Thus, it is necessary to maintain the mixture within the electric field for a certain period of time to cause the proper agglomeration and depositing of the wax contained in the mixture. In view of the above-mentioned high electric intensity it has been customary to construct the electric treaters so that the electric field, i. e., the gap between the positive and negative electrodes, is comparatively small. With such small gaps it is obvious that the depositing of the wax on either or both vided for the passage of the mixture, and finally completely closes said gaps. Such gradual diminishing of the gap naturally changes the velocity of the mixture passing therethrough, thus changing the above-described time element and causing an insufiicient depositing of the wax so that the oil solution removed from such treaters still contains considerable quantities of wax.

It is therefore one of the objects of the present invention to avoid the above-described defects and to provide a method and means for treating a wax-containing chilled oil solution by passing it continuously through an electric field, and simultaneously and continuously removing and withdrawing the wax depositing on the electrodes.

It is a further object of the present invention to provide a structure wherein all of the oil solution to be treated is caused to pass through the electric field.

} electrodes gradually diminishes the space pro- The above and other objects may be attained by continuously scraping off the wax deposited on the electrodes, thus causing the agglomerated wax to settle out more rapidly to the bottomof the treater from whence it is removed as by means of a wax pump. The scrapers may also act as baiiles to cause the wax and oil mixture to pass into the electric field, the oil solutionbeing withdrawn through some of the electrodes, thus preventing any removal of untreated and wax-containing oil. f'

Therefore, broadly stated, the invention resides in passing the chilled mixture of oil and wax through an electric field of a sufliciently high intensity and at 'a rate suflicient to cause the wax contained therein to deposit on one or more electrodes, and to continuously remove the thus deposited wax to maintain constant the electric gap and thus permit a sumcient period of treatment for the oil being dewaxed.

The invention further resides in the removal of the treated oil through one set of electrodes, thus insuring'a treatment of all of the oil before its removal from the electric treater.

More particularly stated, the invention resides in an electric treater, means for introducing the waxy chilled oil into said treater, means within treated oil, these means being located so that the oil being treated must first pass through the electric field before it reaches these discharging means.

In its preferred form theinvention comprises an electric treater, a pipe leading into said treater andv adapted to introduce thereinto the waxy chilled oil either with or without a diluting agent, a vertically disposed rotating electrode within the treater, a plurality of hollow segmental electrodes of an opposite polarity disposed around the rotating electrode and arranged at a proper distance therefrom to create the necessary gap,

openings within said segmental electrodes communicating the interior thereof with the gap,

means associated with the segmental electrodes.

Figure 3 is a vertical section through a modi-- fled form of an electric treater; and

Figure 4 is a section taken along line 6- 5 0 Figure 3.

Referring more particularly to Figures 1 and 2, v

is held in place by a shaft l9 attached thereto,

'said shaft passing out through coverv l3 through .a stufling box 20 and being provided at its upper end with actuating means 2| adapted to rotate shaft l9 and the cylindrical electrode l8. Two 4 hollow segmental electrodes 22 are disposed around and on opposite sides of the central electrode l8, said electrodes 22 being arranged so as to leave a space on gap 23 between the faces of electrodes I8 and 22. The inner faces of the hollow electrodes 22 are provided with a plurality of openings 24. Electrodes 22 are further provided with pipes 25 adapted to withdraw the treated oil entering the hollow electrodes, said pipes .25 being equipped with insulators 2B. The electric potential is conducted to the electrodes 22 through a wire 30, insulator 3|, and wires 32 and 33, and the electrical return circuit completed through the ground or through conductor 34 to the electricity-generating means not shown in the drawings. In the latter case as is obvious, the wires 30 and 34 are attached to the opposite poles of the generating means. A plurality of scrapers 35 are rigidly attached to the inner walls of chamber III, the other ends of said scrapers abutting against the rotatable electrode Hi.

In operation, the wax-bearing oil, having been previously diluted and chilled to a temperature at which the wax, or a substantial portion thereof, has precipitated from the solution, is introduced at a predetermined rate through pipe l2 into chamber l0. Simultaneously, electrode I8 is caused to be rotated by the rotation of the actuating means 2|, and an electric potential of a high intensity is impressed through wires 30, 32 and 33- to the electrodes 22. As stated previously, the intensity of said potential must be such that the desired potential gradient of from 5,000 to 35,000 volts per inch is maintained through the electric field or gap 23 separating electrodes 22 and I8. The chilled oil and wax mixture entering chamber l 0 passes into the electric field 23 wherein the precipitated wax particles are acted upon by the electric field.

Assuming that the electric particles are originally negatively charged, the electric potential impressed upon this system is such that electrode I8 is charged positively while the stationary elec-- trodes 22 are charged negatively. With such a system and by a proper regulation of the gap or electric field 23 and the rate of flow of the chilled mixture therethrough, the waxy particles in the mixture are caused to be agglomerated and deposited on the electrode having the polarity opposite to that of the waxy particles, i. e., the positive rotating electrode 18. The diluted oil thus freed from the wax particles then passes through openings 24 into the interior of the electrodes 22 and is then removed therefrom through the oil outlet pipes 25.

As stated previously, the thickness of the accumulation of the wax deposited on electrode l8 decreases the clearance or the size of the passageway between the electrodes, increasing the rate of travel of the oil-wax mixture through the treating field, thus decreasing the duration of treatment and preventing the proper separation and deposition of the wax. To avoid this the continuous rotation of the cylindrical electrode I8 is provided for the purpose of removing the wax thus deposited on said electrode, this removal being accomplished by the scrapers 35. abutting against the surface of this electrode. It is obvious that such a removal or scraping of I the wax from the cylindrical surface of the electrode l8 permits the maintenance 'of a proper electric field or gap 23 and of a constant rate of flow of the mixture therethrough, thus causing a proper agglomeration and depositing of the wax and the separation thereof from the oil being treated. The wax scraped from the rotating electrode by the scrapers 35 falls down into the conical bottom I4 of chamber I and is removed therefrom through discharge line l6 by means of the wax pump l5.

The location of the oil discharge openings 24 within the electric field, as well as of the oil outlet lines 25 formed within the interior of the electrodes 22 forces all of the oil being treated to pass through the electric field, thus preventing any untreated oil still containing the wax precipitate from passing into the discharge line. This passage of the oil-wax mixture through the electric field is further aided by the positioning of the scrapers 35.

Instead of providing a single rotating electrode for the depositing of the wax, a series of rotating belts of steel may be placed between the stationary electrodes. This is shown more particularly in Figures 3 and 4. In these drawings, the treater 50, similar to the one shown and described in conjunction with Figures 1 and 2, and similarly provided with an inlet line 52 for the chilled waxy oil and a wax discharge line 53 and wax pump 54, contains a series of vertically aligned electrodes 'which alternate in polarity. Thus, the stationary electrodes 55, 55, and 51 areof one polarity, while the electrodes 58 and 59 are of the opposite polarity, thus permitting an electric field in the spaces or gaps between said electrodes. Like the stationary electrodes 22 of Figure l, electrodes 55, 56, and 51 are of hollow construction and are provided with a plurality of openings 60 communicating the interior of said electrodes with the above-mentioned gaps between the electrodes of opposite polarity. The upper ends of these stationary electrodes communicate with a pipe leading out of the treater 50.through an insulator 62. The electric potential is impressed through wires 63 and 64 the latter being attached to pipe 6| within the treater 50. Wire 63 passes into the treater through an insulator 65. As stated above, the movable electrodes consist of thin strips or belts oisteel passed over rollers and forming the well-known endless belts. The rollers 10 in turn are set on shafts II, the ends of which rest in bearings 12 in the side-walls of the electric treater 50. One end of each of the shafts ll supporting the upper rollers 10 passes out of the treater 50 through stuffing boxes 13. These ends are provided with means for the actuation of the endless belts forming the moving electrodes 58 and 59. As shown more particularly in Fig. 4, this actuating means consists of sprocket wheels 14 actuated by a chain 15. It is clearly obvious that the actuation or rotation of the sprocket wheels 14 will cause a corresponding movement of the shafts II and drums 10 to which these wheels are attached, thus causing the movement of the endless belts of steel which form the electrodes 5B and 59. Treater 50 is grounded through wire 16. i

The operation of the above-described structure is similar to that of the structure shown in Figures 1 and 2 and is clearly obvious. Thus, the chilled oil entering treater 59 through line '52 passes into the electric fields created by the passage of a current of a sufiiciently highpotential gradient through line 63. The waxy oil is thus treated in said electric fields and the waxy particles are caused to deposit on the steel belts forming the electrodes 58 and 59, while the oil thus freed from the wax passes through the openings 60 into the interior of the stationary electrodes and is discharged from the treater through line 6|. As stated previously, the accumulation of the wax on the electrodes 58 and 59 will cause a closing of the electric gap or field, thus preventing a proper treatment of the waxy oil. ,For this purpose scrapers 80 are provided. These scrapers are rigidly attached to the walls of the treater and abut against the strips of steelforming the electrodes 58 and 59. Obviously, the movement of said strips of steel will cause the scraping off of the wax precipitated and deposited thereon, said agglomerated wax falling down into the bottom of the treater 50 and being removed therefrom through line 53 by means of the wax pump 54. It is clearly obvious that the polarity of the stationary and of the movable electrodes must be selected so that the wax will deposit on the moving electrodes 58 and 59.

In the case where the polarity of the wax particles is such that an electric treatment of the oil containing such wax causes it to deposit on the electrodes of both polarities, it is obvious that the structures described hereinabove must be modified so as to move or rotate both sets ofelectrodes and to scrape the wax deposited thereon. It is also obvious that the above type 'of structures for the electrical depositing of the wax precipitate may be used with chilled waxy oils both in the diluted and undiluted state. This dilution of the wax-bearing oil is, however, frequently preferable due to the fact that the diluted oils require a lesser chilling for the precipitation of the wax therefrom.

Naphtha, gasoline, liquid propane, acetone, and benzol, methyl chloride, halogenated hydrocarbons, ethers, etc., may be employed as diluents for the wax-bearing oil.

The process and apparatus described hereinabove are not limited to the treatmentof wax, but are also applicable to asphalt, asphaltines, petrolatum, sludges, and other substances, both solid and plastic.

It is to be understood that the above disclosures are not to be considered as limiting but merely descriptive of the generic invention and that many variations may be made by those skilled in the art within the scope of the appended said electrodes, withdrawing oil from which wax has been separated through the other electrode and removing wax from the electrode on which wax was deposited.

3. A method for dewaxing oils which comprises passing a mixture of oil and wax through an electric field between a plurality of electrodes in substantial contact therewith, depositing wax on certain of said electrodes, withdrawing dewaxed oil from said electric field through certain of other electrodes and removing wax deposited on said electrodes.

4. In an apparatus for dewaxing wax-bearing oils, a chamber, a series of alternatingly positive and negative electrodes, means to impress an electric potential upon said electrodes whereby wax is permitted to deposit upon electrodes of one polarity, means to move said last mentioned electrodes and means to withdraw, dewaxed oil through electrodes of opposite polarity.

5. In an apparatus for dewaxing wax-bearing oils, a chamber, a series of altematingly positive and negative electrodes, means adapted to pass waxy 011 between said electrodes, means to impress an electric potential upon said electrodes whereby wax is permitted to deposit upon electrodes of one polarity, means to move said last mentioned electrodes, scraping means communicating with said moving electrodes and adapted to remove therefrom wax depositing thereon and -means to withdraw dewaxed oil through electrodes of opposite polarity.

6. An apparatus for dewaxing wax-bearing oils which comprises a. chamber, a plurality of vertical electrodes within said chamber, means associated with said electrodes and adapted to impress an electric field between said electrodes, means i for passing wax-bearing oil in the space between said electrodes whereby wax is deposited on one ofsaid electrodes, means for removing wax deposited on said electrode and dropping said wax to the bottom of said chamber and means for withdrawing oil from which wax has been re-- moved through the other electrode.

7. An apparatus as in claim 6 in which the means for withdrawing oil from which wax is comprising a chamber, a plurality of hollow stationary electrodes disposed within' said chamber, moving electrodes disposed within said chamber, between each pair of stationary electrodes and without contact with said stationary electrodes,

said hollow stationary electrodes being provided with means for the removal of dewaxed oil from the spaces between the stationary and moving electrodes, means in communication with the chamber adapted to pass the wax-bearing oil through the spaces between said electrodes,

adapted to impress an electric field on the oil passingbetween said electrodes and to cause the depositing of the wax precipitate, and scraping means in engagement with the moving electrodes adapted to remove therefrom the wax depositing thereon.

10. An apparatus for dewaxing wax-bearing oils comprising a chamber, an imperforate electrode disposed axially within said chamber, means in mechanical engagement with said electrode adapted to rotate the same, a plurality of hollow stationary electrodes disposed around the rotating electrode and without contact therewith, said hollow stationary electrodes being provided with means for removing dewaxed oil passing between the stationary and rotating electrodes, means in communication with the chamber adapted to pass a chilled wax-bearing oil through the space between the stationary and rotating electrodes, electric means in engagement with the electrodes adapted to impress an electric field across said space, and scraping means associating with the rotating electrode adapted to remove therefrom the wax depositing thereon.

11. In a structure according to claim 8 wherein the movable electrodes each comprise a strip 01' steel in the form of an endless belt, rollers for said endless belt and means in mechanical engagement with said rollers to rotate the same and move the steel electrode.

12. In an apparatus for dewaxing wax-bearing oils, having electrodes disposed therein, means for moving certain of said electrodes, meansfor passing the wax-bearing oil between the moving and stationary electrodes, means for impressing an electric field between said electrodes and for.

depositing of the wax on the moving electrodes, means in engagement with said moving electrodes adapted to remove therefrom continuously the wax deposited thereon, and means for withdrawing dewaxed oil through said stationary electrodes.

13. In an apparatus for dewaxing wax-bearing oils, a chamber, a plurality of stationary electrodes disposed within said chamber, a plurality of movable electrodes disposed between the stationary electrodes, means in electric engagement with said stationary and movable electrodes adapted to impress an electric field between said electrodes, scraping means in mechanical engagement with the movable electrodes adapted 'to remove therefrom the substances depositing thereon, and means cooperating with the stationary electrodes adapted to remove the dewaxed oil through said stationary electrodes from the spaces between the stationary and moving electrodes.

h BLAIR G. ALDRIDGE.

BASIL HOPPER.

means in electric engagement with the electrodes 

